Structure

Synthesis and secretion

Types of receptors and intracellular hormonal signal transduction systems

V 1A and V 1B receptors are associated with G q proteins and stimulate the phospholipase-calcium mechanism of hormonal signal transmission.

V 1A receptors (V 1 R) are localized in vascular smooth muscle and in the liver; agonists of these receptors are cognitive stimulants and eliminate disturbances in spatial memory caused by scopolamine; antagonists impair memory recall. The use of these substances is limited by the route of administration. Examples of V 1 R agonists that act on memory include NC-1900 and AVP 4-9 .

V 1B (V 3) receptors are expressed in the anterior pituitary gland (“adenopituitary gland”) and the brain, where vasopressin acts as a neurotransmitter. They are responsible for behavioral and neuroendocrine adaptation to stress and are also involved in some psychiatric conditions, particularly depression. The study of these receptors occurs mainly using the selective antagonist SSR149415.

V 2 receptors are associated with G s proteins and stimulate the adenylate cyclase mechanism of hormonal signal transmission. Localized mainly in the collecting duct of the kidney. These receptors are the target of many drugs to combat diabetes insipidus. In the central nervous system, these receptors may be a target for combating cognitive disorders, but the only substance that has been the subject of detailed research is the agonist of these receptors DDAVP (desmopressin, 1-deamino-8-D-arginine-vasopressin), which enhances memory and cognitive abilities.

Physiological effects

Vasopressin is the only physiological regulator of water excretion by the kidney. Its binding to the V 2 receptors of the collecting duct leads to the integration of the water channel protein aquaporin 2 into its apical membrane, which increases the permeability of the epithelium of the collecting duct for water and leads to increased reabsorption. In the absence of vasopressin, for example in diabetes insipidus, a person’s daily diuresis can reach 20 liters, whereas normally it is 1.5 liters. In experiments on isolated renal tubules, vasopressin increases sodium reabsorption, whereas in whole animals it causes an increase in excretion of this cation. It is still not clear how to resolve this contradiction.

The final effect of vasopressin on the kidneys is an increase in body water content, an increase in circulating blood volume (CBV) (hypervolemia) and dilution of blood plasma (hyponatremia and decreased osmolarity).

Through V 1A receptors, vasopressin increases smooth muscle tone internal organs, especially the gastrointestinal tract, increases vascular tone and thus causes an increase in peripheral resistance. Due to this, as well as due to the increase in blood volume, vasopressin increases blood pressure. However, at physiological concentrations of the hormone, its vasomotor effect is small. Vasopressin has a hemostatic (hemostatic) effect due to spasm small vessels, as well as due to increased secretion from the liver, where V 1A receptors are located, of some blood coagulation factors, especially factor VIII (von Willebrand factor) and the level of tissue activator plasmin, increased platelet aggregation.

In the brain, it is involved in the regulation aggressive behavior, apparently increasing aggressiveness.

Regulation

The main stimulus for the secretion of vasopressin is an increase in the osmolarity of the blood plasma, detected by osmoreceptors in the paraventricular and supraoptic nuclei of the hypothalamus, in the region of the anterior wall of the third ventricle, as well as, apparently, the liver and a number of other organs. In addition, hormone secretion increases with a decrease in BCC, which is perceived by the volume receptors of the intrathoracic veins and atria. Subsequent secretion of AVP leads to the correction of these disorders.

Vasopressin is chemically very similar to oxytocin, therefore it can bind to oxytocin receptors and through them has a uterotonic and oxytocin (stimulating the tone and contractions of the uterus) effect. However, its affinity for OT receptors is low, therefore, at physiological concentrations, the uterotonic and oxytocic effects of vasopressin are much weaker than those of oxytocin. Similarly, oxytocin, by binding to vasopressin receptors, has some, albeit weak, vasopressin-like effects - antidiuretic and vasoconstrictor.

The level of vasopressin in the blood increases with states of shock, injuries, blood loss, pain syndromes, with psychosis, when taking certain medications.

Diseases caused by dysfunction of vasopressin

Diabetes insipidus

In diabetes insipidus, the reabsorption of water in the collecting ducts of the kidneys decreases. The pathogenesis of the disease is caused by inadequate secretion of vasopressin - ADH (diabetes insipidus of central origin) or a reduced response of the kidneys to the action of the hormone (nephrogenic form). Less commonly, diabetes insipidus is caused by accelerated inactivation of vasopressin by circulating blood vasopressinases. During pregnancy, the course of diabetes insipidus becomes more severe due to increased vasopressinase activity or weakened sensitivity of the collecting ducts.

Patients with diabetes insipidus excrete per day large number(>30ml/kg) dilute urine, are thirsty and drink a lot of water (polydipsia). To diagnose central and nephrogenic forms of diabetes insipidus, the vasopressin analogue desmopressin is used - it has therapeutic effect only with the central form.

Vasopressin is hormonal substance, which regulates the process of removing fluid from the body. This is the only element that performs this function in the human body.

During development various pathologies the synthesis of this hormone may be impaired, leading to uncontrolled diuresis. Let's try to figure out what the hormone vasopressin is, where it is produced and why our body needs it.

Main characteristics and features of vasopressin

First, let's figure out what it is - antidiuretic hormone.

This substance has protein structure, and consists of 9 amino acids. It is destroyed quite quickly (in less than half an hour) in the kidney and liver cells, so the process of its production is regular and cyclical.

Where is it synthesized?

Where is vasopressin produced? ADH is a substance that is synthesized by the cells of the hypothalamus. After this, it penetrates the posterior lobe of the cerebral pituitary gland, where its concentration gradually increases. And only from the pituitary cells is it released into the blood in the required quantity.

It has been proven that the antidiuretic hormone vasopressin is also produced by the gonads, but in limited quantities. However, still the essence and purpose this process remains unknown.

Main features of the hormone

ADH is a substance that not only has an antidiuretic effect. This element also affects more serious functions of the body. In particular, on the production of ACTH.

The hormone takes part in many processes and affects various organs and systems. For its active production, special conditions must be created. This could be stress, fear, strong anxiety, gastrointestinal pathologies, accompanied by excessive vomiting or diarrhea, during which the human body loses a large amount of fluid, etc. When water balance is restored, the cells of the hypothalamus gradually reduce the amount of ADH produced to normal limits.

As you can see, antidiuretic hormone is a multifunctional substance that is extremely important for full functioning endocrine system. But its functions are not limited to this, so they should be considered in more detail.

Functional tasks of the ADG

Biological functions vasopressin are:

• stimulating the process of fluid reabsorption in the kidneys;
• reducing the amount of sodium in the body;
• increasing blood volume in blood vessels;
• increasing the volume of water in the body;
• regulation of blood pressure (in particular, the hormone helps to increase it);
• memory stimulation;
• improving learning ability;
• control of social behavior.

These are the main effects of vasopressin, but there are a few more aspects to be aware of. The hormone affects the concentration of urine and reduces its volume. Thus, only required quantity waste liquid, and all useful substances remain in cells and tissues. It follows from this that vasopressin has an antidiuretic effect.

In addition, the hormone has hemostatic properties, as it improves blood clotting. This is achieved due to spasm of blood vessels caused by the activity of this substance. Its production increases significantly in stressful situations, in states of shock, pain syndromes and intense bleeding.

This is interesting. Vasopressin is called the fidelity hormone. And this is quite justified, since when it is sufficiently present in a person’s blood, not only social, but also family behavior is formed. This means that men and women who do not suffer from a deficiency of this substance are more attached to loved ones (especially their spouse) than those whose hypothalamus secretes insufficient amounts of it.

Thus, having studied the mechanism of action of vasopressin and its main tasks in the human body, we can conclude that many things occur with its direct participation. important processes. Any deviations from the norm may lead to serious disorders, and also signal health problems.

Lack of vasopressin

If the process of hormone secretion is disrupted, ailments occur, which should be the reason for contacting a therapist or endocrinologist. In this case, it is carried out clinical analysis on vasopressin, which may show a decrease or increase in its level.

In addition, it is important to evaluate the condition of the kidneys, for which a urine test is performed. A biochemical blood test is needed to determine the concentration of potassium, sodium and chlorine in the body. If the test results are alarming, the patient is sent to CT and MRI to clarify the diagnosis.

Reasons for deviations

If, when deciphering research data, hyperfunction of vasopressin was revealed, then often such a violation of its secretion indicates the development pathological processes in the body. One of rare diseases, But common reasons A similar anomaly is Parhon's syndrome. This deviation is also called syndrome of inappropriate secretion of antidiuretic hormone.

This pathology can result from:

• intense bleeding accompanied by large blood losses;
• uncontrolled or long-term use diuretics;
• hypotension, etc.

Much more dangerous are cases when excess vasopressin is caused by malfunctions of the pituitary gland due to the formation of cancerous tumors. In addition, a jump in indicators is often observed in patients suffering from pulmonary tuberculosis, asthma, and pneumonia. Diseases of the central nervous system can also lead to a similar deviation.

As vasopressin secretion increases, diuresis decreases significantly. Urine becomes darkish, concentrated, and contains increased amount sodium Consequently, its content in the blood decreases, which can lead to serious complications.

Reasons for decreased hormone levels

Decreased ADH secretion is observed in patients with diabetes insipidus. The disease can be triggered by malfunctions of the hypothalamic-pituitary system, as well as a decrease in the sensitivity of renal receptors to the effects of this hormone.

With a lack of vasopressin, severe, difficult to quench thirst, migraine attacks, sharp decline body weight, dryness of the epidermis, viscosity of saliva and a decrease in its volume, frequent urge to vomiting, increased body temperature. The patient exhibits hypotension, so doctors often resort to the use of vasopressors to normalize it.

It is important to pay attention to the amount of urine excreted per day. With ADH deficiency, the urge to urinate sharply increases, and during each bowel movement bladder a fairly large volume of urine is released. This leads to dehydration and the body loses many useful substances. And this condition is very dangerous, and is fraught with serious complications!

How to increase vasopressin?

Methods for normalizing the level of this hormone directly depend on the reasons for its decrease. Removal of the tumor, taking antibiotics for infectious etiologies of the disease, using drugs to treat pathologies cardiovascular system- all these measures may well stabilize the situation and lead to complete cure.

But sometimes it is possible to restore functions and establish the production of the fidelity hormone vasopressin only with lifelong hormone therapy. Specific medications can only be prescribed by a doctor. When developing a treatment regimen, many factors are taken into account that the patient himself cannot take into account. This concerns, first of all, the presence of accompanying chronic diseases(in addition to those that may cause vasopressin deficiency).

Pharmacological agents based on vasopressin are an integral part of the treatment regimen for diabetes insipidus. They help reduce the amount of urine excreted per day, normalizing the functioning of the kidneys.

Thus, having studied the mechanism of action of ADH, determined its main functions and possible reasons deviations, we can conclude that this hormonal substance, along with others, plays important role for coordinated work human body. You cannot ignore any ailments, because if they have a persistent course, this is one of the the brightest signs that serious disruptions have occurred in the human body. Stability hormonal levels– one of the main indicators of health, and this must always be remembered!

Antidiuretic hormone or vasopressin is a microelement that regulates the removal of water from the body. If it occurs in the body hormonal imbalance and the antidiuretic hormone, for some reason, does not perform its functions, then a person can lose up to 20 liters of water with urine. At the same time, he considers 1-2 liters to be the norm. Thus, antidiuretic hormone protects a person from death caused by dehydration. Unfortunately, there are no analogues of antidiuretic hormone in the body. This item biochemical metabolism is the only one.

Antidiuretic hormone is synthesized by the hypothalamus, which is part of the endocrine system. Along with the pituitary gland, adrenal gland and thyroid gland. Vasopressin is a hormone that does not immediately enter the blood, but accumulates first in the pituitary gland. It enters the bloodstream only after reaching a critical level.

Antidiuretic hormone or vasopressin not only removes water through the kidneys, it also generally regulates the amount of blood by diluting the plasma. The action of antidiuretic hormone is quite simple - it increases the permeability of the walls of the collecting ducts in the kidney parenchyma. During filtration, the liquid returns to the bloodstream, and waste and heavy elements go into urine.

If there is no antidiuretic hormone in the body, then primary urine simply exits through the kidneys, along with proteins and useful minerals. The kidneys are capable of passing up to 150 liters of primary urine per day. A lack of vasopressin can lead to a very quick and painful death in a person.

There are some functions not related to the removal of fluid, but no less important for humans:

1. ADH has a positive effect on smooth muscle tone. This affects the functioning of the gastrointestinal tract.
2. Under the influence of ADH, the heart and large vessels work better.
3. Vasopressin and oxytocin regulate blood pressure, especially at the periphery of the circulatory system.
4. By causing spasms of small vessels in damaged areas, vasopressors quickly stop bleeding. Therefore, these substances are produced by the body as a result of stress, physical injury or pain.
5. Vasopressors affecting blood vessels, which end in arteries, can raise blood pressure. This in itself is not dangerous, unless the person is a chronic hypertensive patient.
6. The formula of the hormone vasopressin allows it to influence the central nervous system. Thus, vasopressors evoke paternal instincts in men, suppress outbursts of aggression and help a man choose a life partner. For this last feature, I call this microelement the fidelity hormone.

Diagnosis of ADH level disorders

The broad mechanism of action of ADH forces one to quite accurately determine its level in the blood, and most importantly, find it in as soon as possible, the reasons for its increase or decrease. To do this, it is not enough to simply take a blood test to determine the content of antidiuretic hormone.

In addition, the patient must donate blood and urine for biochemical analysis, as a result of which the amount of potassium, sodium, chlorine and other microelements is determined. A test for aldosterone, a hormone secreted by the adrenal glands and regulating water-salt metabolism, is required. The quality of blood is determined by the amount of cholesterol, creatinine, protein, and calcium in it. If there is a suspicion of a malfunction of the pituitary gland or hypothalamus, the patient is referred to computed tomography. During this process, doctors try to determine the presence of a tumor in the brain.

Abnormal vasopressin

Increased or reduced content vasopressin in the blood is equally dangerous to health. When an excess of a trace element is detected in the blood, a number of diseases are suspected:

1. Parhon's syndrome. This pathology provoked by severe blood loss, a diuretic, and a decrease in blood pressure. In general, for all reasons that can disrupt the balance of water and salt in the body.
2. An increase in hormone levels can occur under the influence of a tumor-affected pituitary gland. A neoplasm may not even arise in the pituitary gland itself, but next to it, but at the same time compress it, causing disturbances in the levels of microelements secreted by it.
3. Disturbances in hormone levels in the blood can cause systemic diseases– pneumonia, asthma, tuberculosis.

The role of vasopressin in the body is difficult to overestimate. Its shortage is an overabundance, immediately manifests itself external signs– nausea, vomiting, convulsions, loss of consciousness. In severe cases, swelling of the brain occurs, body temperature drops, and the patient falls into coma. The heartbeat slows down, breathing stops and death occurs.

If a person experiences a decrease in vasopressin levels, then most likely he has developed such pathologies;

1. Not diabetes.
2. Tumor in the pituitary gland or hypothalamus.
3. The kidneys have lost sensitivity to antidiuretic hormone.

As a result of ADH deficiency, a person begins extreme thirst, a strong headache, the skin becomes thin and dry, body temperature rises, and vomiting may occur. The patient rapidly loses body weight. But the main manifestation of the disease is increased urine output. After all, what is ATG? A microelement that regulates the outflow of urine, and if there is little of it in the blood, then urine is released in an uncontrolled flow.

Principles of treatment

The doctor decides how to increase or decrease the level of antidiuretic hormone. Based on a comprehensive study of the reasons that caused the deviation from the norm.

During therapy, the body has a supporting effect with the help of drugs that retain urine, or, if necessary, help to excrete it. "Demeclocycline", as a central ADH blocker, normalizes the functioning of the kidneys, which are under the influence of vasopressin. There are other diuretics for this purpose, but they are all prescribed by a doctor. He's counting correct dosage and a dosage regimen based on test results.

The main thing you need to understand is hormone therapy, this is only a temporary measure. To eliminate a violation of the microelement norm in the blood, it is sometimes necessary to undergo a long course of treatment or even surgery. After all, such a situation with a violation of the level of ADH can be caused by syphilis, vascular diseases, a benign or malignant tumor in the pituitary gland or in another part of the brain. Any treatment should only be prescribed by a specialist. In situations where it comes to hormonal drugs, any self-medication may end severe complication or even the death of a person.

Antidiuretic hormone or vasopressin hormone is a peptide. It contains nine amino acid residues. Its half-life is 2-4 minutes. This hormone is produced in the large cell parts of the hypothalamus, and from there it is transported to the neurohypophysis. Movement is carried out along axons thanks to special carrier proteins.

Functions of the hormone vasopressin

The main activity of the hormone is the control of water metabolism. That's why it is called antidiuretic. As soon as the amount of ADH in the body increases, the volume of urine excreted decreases sharply.

But in reality, it turns out that vasopressin is a multifaceted hormone and performs an impressive number of functions in the body. Among the most important of them:

• an increase in the volume of blood circulating through the vessels;
• increased smooth muscle tone;
• increased activity of blood cells platelets;
• correction of memory mechanisms;
• reducing the amount of sodium in the blood;
• oxidation of fatty acids.

Vasopressin norms

If the test results indicate that the amount of vasopressin is normal, there is no cause for concern. Normal reference values ​​look like this:

• with plasma osmolality 270-280 mOsm/kg –
• 280-285 mOsm/kg –
• 285-290 mOsm/kg – 1-5 pg/mol;
• 290-295 mOsm/kg – 2-7 pg/mol;
• 295-300 mOsm/kg – 4-12 pg/mol.

According to the principle of action, the hormones vasopressin and can be considered very similar. Their main difference is that the latter contains two fewer amino acid residues. But this does not prevent the hormone from exhibiting higher activity in relation to stimulation of milk secretion, for example.

Hypofunction of the hormone vasopressin

If there is not enough substance in the body, diabetes insipidus may develop. The disease is characterized by inhibition of the function of reuptake of water by the renal tubules. The use of ethanol and glucocorticoids contributes to a decrease in ADH levels.

Hyperfunction of the antidiuretic hormone vasopressin

ADH can be intensely produced when:

The problem manifests itself as a decrease in the density of blood plasma and the release of very high concentrations of urine.

ADH is a peptide consisting of 9 amino acid residues. It is formed in the supraoptic nucleus of the hypothalamus. Through the portal system of the pituitary gland, this peptide enters the posterior lobe of the pituitary gland, concentrates there and is released into the blood under the influence of nerve impulses entering the pituitary gland. The release of ADH from storage vesicles into the neurohypophysis is regulated primarily by plasma osmolarity. If plasma osmolarity rises above a critical level, the release of ADH sharply accelerates. A rapid increase in plasma osmolarity by only 2% leads to a 4-fold increase in ADH secretion, while a decrease in osmolarity by 2% is accompanied by a complete cessation of ADH secretion. Hemodynamic factors also have a pronounced regulatory effect on the output of ADH. An increase in secretion is observed with a decrease blood pressure. Despite the relegation osmotic pressure, ADH secretion turns out to be enhanced by an excessive decrease in the volume of extracellular fluid, acute blood loss, stress, pain, administration of barbiturates, analgesics. ADH has a daily rhythm of secretion, secretion increases at night; decreases in supine position, when moving to a vertical position, its concentration increases.

The target of ADH is the wall of the distal tubules of the kidneys, where it enhances the production of hyaluronidase. The latter, depolymerizing hyaluronic acid, increases the permeability of the tubule walls. As a result, water from the primary urine passively diffuses into the kidney cells due to the osmotic gradient between the hyperosmotic intercellular fluid of the body and the hypoosmotic urine.

Diabetes insipidus is a water metabolism disorder caused by a primary disturbance in the production of ADH due to infectious or traumatic damage to the hypothalamus or obstruction of the portal system of the pituitary gland by a tumor. To restore normal fluid content in the body, patients, prompted by a feeling of thirst, drink large quantities liquids. ADH deficiency can be complete or partial, which determines the degree of polydipsia and polyuria. Dynamic tests are used to differentiate insufficient ADH production (diabetes insipidus) from renal ADH resistance (renal diabetes insipidus) or excess water intake (psychogenic polydipsia). When performing a water restriction test in patients with severe ADH deficiency, plasma osmolarity increases, but urine osmolarity usually remains below it. After administration of vasopressin to such patients, urine osmolarity rapidly increases. With mild ADH deficiency and polyuria, urine osmolarity during the test may be slightly higher than plasma osmolarity, and the response to vasopressin is weakened.

Constantly low levels Plasma ADH indicates severe neurogenic diabetes insipidus; subnormal levels in combination with plasma hyperosmolarity indicate partial neurogenic diabetes insipidus.

Increased ADH secretion is observed in the syndrome of inappropriate vasopressin production or Parhon's syndrome. Parhon's syndrome is the most common variant of impaired ADH secretion, characterized by oliguria, lack of thirst, the presence of general edema, and weight gain. It is important to distinguish the syndrome of inappropriate vasopressin production from other conditions: congestive heart failure, renal failure, glucocorticoid deficiency, hypothyroidism, taking medications that stimulate ADH. Patients with the syndrome of inappropriate vasopressin production usually exhibit a decrease in plasma sodium, high urine osmolality relative to plasma osmolality, and decreased excretion in response to fluid load.

Ectopic ADH secretion occurs in a wide variety of tumors of the APUD system. Most often, ectopic ADH secretion causes malignant bronchogenic lung cancer, malignant tumors pancreas, pancreas thymus glands, duodenum.

When conducting research, it is necessary to take into account that during long-term storage, significant decomposition of ADH occurs. Plasma samples should not be at room temperature.